Monday, December 12, 2016

A Dynamic Approach to Factor Allocation

ETF Trends (hat tip Josh) showed the following "quilt" of large cap factor calendar year returns in the post Low Volatility is Not a Buy and Hold Strategy.

Author John Lunt's takeaway (bold mine):
It is reasonable to conclude that low volatility is not a buy and hold strategy. This is not because it is unlikely to outperform over the long term, but rather because few investors are likely to survive multiple years of underperformance. Recent months have witnessed money flowing out of the low volatility and minimum volatility ETFs. Is this money flowing into different factor ETFs, or is it moving back to the market cap-weighted ETFs? Rather than abandoning factors during their periods of underperformance, investors may want to consider the opportunities that exist in factor blending and in factor rotation.
I agree completely and in this post I'll outline one potential framework to allocate to factors that diversifies across a few approaches and across time. Update: following my publishing of this post I received a comment that a lot of the work in the below was built out in further detail in a white paper by Ronald Balvers and Yangru Wu titled Momentum and Mean Reversion Across National Equity Markets. I recommend anyone interested in the framework to take a deeper look there.


For simplicity, I used the same indices outlined in the ETF Trends post with the exception of the below two tweaks:
  1. I added a small cap index (S&P 600 Smallcap Index)
  2. I swapped out the S&P 500 Dividend Aristocrat Index for the MSCI USA High Dividend Yield Index; the issue with the S&P 500 Dividend Aristocrat Index for this analysis is that it has a size tilt (it's equal weighted) and a momentum / quality tilt (it holds companies that have increased dividends every year for the last 25 consecutive years built in as well). Neither are a bad thing at all, just not the pure dividend exposure I want for this analysis.
  3. I went back another five years (which does bring up an important boom / bust regime for the analysis)
Similar to what was outlined in the ETF Trend piece, certain factors had more favorable long-term returns over 15 and 20 years (small cap, low volatility, momentum, and high dividend), while high beta and value (of all things) weighed on performance (note that the Russell 1000 Value Index outperformed the S&P 500 Value Index used in the analysis by 100 bps, which shows that getting the factor right may not be enough if you get the implementation part wrong - but I'll save that for another day). 

The below shows the updated factor quilt. Note the quality index only went back 15 years, hence the blank 1996-2000 data.


Intermediate Time Frames: Momentum is the Winner

Momentum tends to work better over shorter periods of look back periods (6, 9, 12 months). The chart below shows momentum and mean reversion using 12-month  returns for the indices and one can see that momentum outperformed over the longer time frame. That said, note that almost all of the outperformance came in the first 10 years as a relative momentum strategy was able to cruise through the bubble.

Longer Time Frames: Mean Reversion is the Winner

Mean reversion on the other hand tends to work better over longer look back periods, in part because valuations tend to matter more over longer time frames (while sentiment is a shorter term signal). We can see that momentum continued to outperform the index over this twenty year period, but not nearly to the extent it had using a shorter signal.

Combining Signals

Given momentum works better over shorter periods and mean reversion works better over longer periods, we can combine the two to diversify allocations by the momentum factor and by time. The result is a portfolio with similar returns, but much more consistent tracking to the S&P 500 (tracking error goes from 9.5% for mean reversion and 8.3% for momentum, to 5.8% for the combination).

Taking it one step further, the below adds cash as an allowable asset class for momentum (i.e. an allocation can only occur if the twelve month return outpaced cash), turning momentum into a more absolute return oriented strategy (mean reversion continues to exclude cash as an asset class).

There are still shorter periods of time in which the blend will underperform, but the blended strategy (with the ability to go to cash) has provided consistent outperformance over three year periods (85%  of the time over the last twenty years). In addition, the relative performance has tended to have a linear relationship with starting valuation (i.e. it tends to outperform going forward when stocks appear relatively expensive) in part because of the ability to move to cash in the case of momentum and in the likelihood of allocating to a less frothy segment of the U.S. stock universe in the case of mean reversion. Something to keep in mind given the current cyclically adjusted P/E "CAPE" has crossed 27x.


Certain factors have shown the ability to outperform over longer periods of time, but can and do underperform over shorter periods. These periods can be challenging for investors that cannot remain disciplined. As a result, a strategy that consistently follows a set of diversified rules to allocate across factors may help reduce behavioral issues of holding onto a strategy that differs from the S&P 500. Given the historical performance of this sort of strategy tends to do relatively better when market valuations are expensive, it may be an interesting approach to allocate across factors going forward.